The present invention relates to an aglucone isoflavone enriched vegetable protein fiber and process for producing the same.
Isoflavones occur in a variety of leguminous plants, including vegetable protein materials such as soybeans. These compounds include diadzin, 60 AC daidzin, daidzein, genistin, 60AC genistin, genistein, glycitin, biochanin A, formonoetin, and coumestrol. Typically these compounds are associated with the inherent, bitter flavor of soybeans, and in the production of commercial products, such as isolates and concentrates, the focus has been to remove these materials. For example, in a conventional process for the production of a soy protein isolate, in which soy flakes are extracted with an aqueous alkaline medium, much of the isoflavones are solubilized in the extract, and remains solubilized in the whey, which is usually discarded following acid precipitation of the protein, to form an isolate. Residual isoflavones left in the acid precipitated protein isolate are usually removed by exhaustive washing of the isolate.
It has been recently recognized that the isoflavones contained in vegetable proteins such as soybeans may inhibit the growth of human cancer cells, such as breast cancer cells and prostrate cancer cells as described in the following articles: "Genistein Inhibition of the Growth of Human Breast Cancer Cells; "Independence from Estrogen Receptors and the Multi-Drug Resistance Gene" by Peterson and Barnes Biochemical and Biophysical Research, Communications; Vol. 179, No. 1, pp. 661-667, August 30, 1992; "Genistein and Biochanin A Inhibit the Growth of Human Prostate Cancer Cells but not Epidermal Growth Factor Receptor Tyrosine Auto-phosphorylation" by Peterson and Barnes: The Prostate 22: pp. 335-345 (1993) and "Soybeans Inhibit Mammary Tumors in Models of Breast Cancer" by Barnes, et al. Mutagens and Carcinogens in the Diet; p. 239-253 (1990).
Of the above isoflavones, several exist as glucosides, or as glucones, with a glucose molecule attached. Several of the glucones such as the 60AC genistin, contain an acetate group attached to the six position of the glucose molecule itself. While all of the isoflavones, including the glucosides are of interest in medical evaluation, the specific isoflavones of most interest are the aglucones, wherein the glucose molecule is not attached. These isoflavones are not as water soluble as the glucones or isoflavone glucosides. Specific isoflavones in this category are daidzein, genistein, and glycitein. These aglucones have the following general formula, ##STR1## wherein, R.sub.1, R.sub.2, R.sub.3 and R.sub.4 may be selected from the group consisting of H, OH and OCH.sub.3. It is therefore to the aglucones and enrichment of a vegetable protein fiber such as the spent flake residue from a soy isolate process with these materials to which the present invention is directed.
It is therefore an object of the present invention to provide an aglucone isoflavone enriched protein fiber, and a process for producing the same. This, and other objects, are specifically achieved in the detailed description of the present invention set forth below.